/SAVEWORLD [-a] [file]
Saves world definitions to file if specified, otherwise from the file named in the body of the WORLDFILE macro.
If "-a" is given, world definitions will be appended to file; otherwise, the world definitions will replace any original contents of file.
Note that when tf starts, it does not automatically read files created with /saveworld. To make it do so, add the /loadworld command to your .tfrc file.
See: worlds, library, /addworld, /load